Preparation of pitch

ABSTRACT

An improved process for preparing petroleum pitch by air blowing residues from catalytic cracking of gas oils is disclosed. Briefly, the improvements comprise (1) use of a heavier feedstock (e.g., a specific gravity above 1.040) and (2) conducting the process in such a manner that only a small amount, preferably substantially none, of the vapors boiling above about 250*F., resulting from the air blowing operation, is vented. As a result of either of these improvements, an increased yield of product is obtained.

United States Patent Ruckel et al.

PREPARATION OF PITCH Inventors: Paul J. Ruckel; Melvin M.

McFeeters, both of Ponca City,

Okla.

Assignee: Continental Oil Company, Ponca City, Okla.

Filed: July 26, 1974.

Appl. N0.: 491,973

Related US. Application Data [63] Continuation-impart of Ser. No. 345,389, March 27,

1973, abandoned.

[52] US. Cl 208/4; 208/6 [51] Int. Cl. C10C 3/04 [58] Field of Search 208/4, 6

[56] References Cited UNITED STATES PATENTS 2,991,24l 7/l96l Renner 208/4 4/1964 Brice et a]. 10 1 967 208/4 Hamner et al. 208/4 Primary ExaminerVeronica OKeefe Attorney, Agent, or FirmBayless E. Rutherford, Jr.

[57] ABSTRACT An improved process for preparing petroleum pitch by air blowing residues from catalytic cracking of gas oils is disclosed. Briefly, the improvements comprise (1) use of a heavier feedstock (e.g., a specific gravity above 1.040) and (2) conducting the process in such a manner that only a small amount, preferably substantially none, of the vapors boiling above about 250F., resulting from the air blowing operation, is vented. As a result of either of these improvements, an increased yield of product is obtained.

10 Claims, No Drawings PREPARATION OF PITCH CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation-in-part of application Ser. No. 345,389, filed Mar. 27, 1973, now abandoned.

BACKGROUND AND FIELD OF THE INVENTION The present invention is in the field of processes for preparing petroleum pitch. It is particularly directed to the preparation of a pitch which is useful as a binder for insulating wallboard.

U.S. Pat. No. 2,991,241 (to Renner) teaches the preparation of a petroleum base pitch having physical characteristics more comparable to coal tar pitch than conventional petroleum asphalts and pitches. According to the process of the Renner patent, the pitch is prepared by air blowing a residue from the catalytic cracking of gas oils, said residue having a maximum API gravity of 18.0. In discussing the Renner patent in the parent application (Ser. No. 345,389) we stated that, since Renner did not teach a minimum API gravity for the feedstock, presumably the minimum API- gravity is zero, which corresponds to a specific gravity of 1.076. Upon further study of the Renner patent, it is believed that Renner teaches that the minimum gravity is an API gravity of 4.5 (lower table in Column 2 and particularly line 41 of Column 2). An API gravity of 4.5 corresponds to a specific gravity of 1.040. Still further, the patent teaches the removal of the lower molecular weight material from the product or in the preparation of the product. In Column 3, lines 25- 28, Renner states: The unreacted lower molecular weight materials are removed concurrently or subsequently by steam stripping, vacuum distillation or solvent (e.g. propane, butane, pentane, etc.) extraction. In the example in Column 3, lines 60-66, Renner makes the statement: Following the initial oxidation the air rate is lowered to about 0.2 cubic foot/hour/lb. of charge and steam admitted to the still at the rate of 0.75 pound per 1.0 pound of overhead oil for stripping the pitch of undesirable wax-oil components representing approximately 50 weight percent on charge." 1

We have discovered a process for preparing a highquality pitch which uses a feedstock having 'a specific gravity higher than 1.040 (and usually higher than 1.076) and which does not require removal of the low molecular weight materials by further distillation. Moreover, our process is conducted in a manner such that only a small amount of higher boiling materials is lost in the process. The combination of these features in our process provides for an increased yield ofpitch,

as compared to the process of the Renner patent.

More particularly, we have discovered that highquality pitches can be prepared from a deeper cut, or heavier bottoms fraction, of the residue from catalytic cracking of gas oils. Since often the feedstock for preparing the pitch is shipped from the. refinery to the vicinity of the wallboard plant, where it is air blown and converted to pitch, it is thus apparent that a substantial saving in freight cost is obtained.

' PRIOR ART A computer search of the prior art resulted in some 49 U.S. patents, most of which were-considered by the agent preparing this application to be irrelevant. The

most pertinent references were U.S. Pat. No. 2,991,241, discussed in the foregoing, and U.S. Pat. No. 3,350,295. The latter patent teaches the preparation of a binder pitch by air blowing a dealkylated heavy catalytic cycle oil. The patent contains no teachings of the properties of the dealkylated heavy catalytic cycle oil. Moreover, the patent teaches that dealkylation is necessary.

In addition to the two patents discussed, the following U.S. patents, produced by the search, are in this general area: U.S. Pat. Nos. 2,802,867, 2,627,498, 2,676,910, 2,755,223, 2,764,523, 2,778,780, 2,870,080, 3,003,943, 3,131,140, 3,350,295, 3,462,359, 3,488,277.

The invention described herein is believed patentable overthe known prior art for the following reason. U.S. Pat. No. 2,991,241 is considered to be the most pertinent art. The discussion of this patent in the foregoing has shown wherein the process described herein is an improvement over the reference.

BRIEF SUMMARY OF THE INVENTION Broadly stated, the present invention is directed to an improved process for preparing petroleum pitch by air blowing of residues from the catalytic cracking of gas oils wherein the improvements comprise:

1. use of a feedstock having a specific gravity above 1.040, and preferably above 1.076, and i 2; conducting the process'in a system wherein only a 7 DETAILED DESCRIPTION Feedstock The feedstock of our invention is a bottoms fraction obtained by the distillation of the cracked oil produced from ,the catalytic cracking of petroleum' gas oils. The term catalytic cracking is'believed to be sufficiently well-known that further description is not needed here.

The cracked oil produced-as a result of the catalytic cracking process is usually subjected to distillation at about 7 to 25 psi pressure to a bottom temperature of about 650 to 750F. The salient feature of our process is using a product which is a deeper cut at this point. The feedstock for use in our process can be obtained by distilling more material overhead or by use of a second distillation of the bottoms fraction wherein the lighter materials are removed. Of course, as wellknown to those skilled in this art, most of the residual catalyst which may be present in the desired bottoms fraction is removed by settling, filtration, or other suitable means.

The feedstock for our process suitably has a specific gravity (/60) above 1.040, more suitably above 1.076, and preferably above 1.09. Based on present knowledge, there is no upper limit for the specific grav- Ity.

A second important feature of the feedstock is percent aromatics present. The percent aromatics as defined herein refer to the use of modified ASTM Procedure D-2549, wherein the saturated solvent is cyclohexane and wherein the l,00OF end point for boiling range is waived. Using this procedure, the percent aromatics in the feedstock is at least 85 weight percent, preferably at least 89 weight percent, and more preferably at least 92 weight percent.

Process Conditions In conducting the process of our invention, the feedstock is heated to a temperature in the range of about 395 to about 650F, preferably about 500 to about 625F, and more preferably 550 to 600F, whereupon it is blown with an oxygen-containing gas such as air.

Using air, the blowing rate is in the range of 0.01 to 5.0 cu ft per hour of feedstock. The blowing rate is dependent on the size of the batch being prepared or the efficiency of air utilization. In the laboratory, a preferable blowing rate is about 2 to about 3 cu ft per hour per pound of feedstock. In commercial size batches, a typical blowing rate is about 0.2 to about 0.8 cu ft per hour per pound of feedstock.

The blowing operation is conducted until the desired softening point of the product is obtained. As is wellknown, a longer blowing time results in a harder product.

An important feature of the process is that it be conducted in a system wherein only a small amount, preferably substantially none, of the higher boiling vapors (i.e., above about 250F) resulting from the blowing operation is vented. The tern small amount as used in the foregoing means a maximum of weight percent, more suitably 5 weight percent, based on the feedstock charge. Usually, and preferably, the maximum amount of higher boiling vapors which are vented is 2 weight percent. From a practical viewpoint, we consider 2 weight percent to be equivalent to substantially none. This feature can be attained either through use of a partial reflux condenser directly over the blowing vessel or by passing the effluent air and vapors through an external partial condenser from which condensed higherboiling vapors are collected and then added back to the feedstock.

An important feature of the process is that the yields are unusually high, in the range of 70 to 98 percent based on feedstock, when making approximately l80F soft point pitch. Yields above 90 percent, on the basis previously defined, can be obtained consistently.

Product of Our Invention The product resulting from our process has the following typical properties for both soft and hard products:

original "ASTM Method N0. D-Zl7l "ASTM Method N0. D-5 "Temp 'I' /gi'aI11/tim|.: in minutes ""ASTM Method No. D-2042 ""ASTM Mcthud Nu. D4398 "ASTM Method N0. D-7O In order to disclose the nature of the present invention more specifically, the following examples, both illustrative and comparative, will be given. It is to be understood that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as these limitations are specified in the appended claims.

EXAMPLE 1 This example shows the advantage of using a heavier bottoms product. A bottoms fraction having a specific gravity of 1.1060 and containing 94 weight percent aromatics was vacuum flashed to remove 21, 40, and 57 percent of the material overhead. The vacuum flashed products were then blown with air at a feedstock temperature of 400575F and an air rate of 2.7 cu ft/hr/lb. The results are summarized below.

Run No. A B C "/1 Material Overhead 2l 40 57 Blowing Time, Hr 20 l6 l3 Feedstock Sp. Gr. 1.122 l.l4l l.l63 Yield, 180 S.P. 84 87 90 For purpose of comparison, by extrapolation the original bottoms product (sp. gr. 1.106) had a yield of 80 percent for a softening point product.

EXAMPLE 2 This example shows the use of a higher specific gravity feedstock increases yield of pitch and decreases the blowing time requirement. The high specific gravity feedstock was prepared by taking a deeper cut into the bottoms fraction of the catalytic cracker fractionation unit. The feedstock temperature and rate of blowing were the same as in Example 1. The results are summarized below:

Run No. D E

Feedstock Sp. Gr. L093 1.132

Converted to I80 Softening Point Yield. "/1 Blowing Time, Hr

EXAMPLE 3 Run No. F G

Reflux No Yes Products Equated for l80F Softening Point Blowing Time, Hr l3 13 Yield, on Feedstock 72" 82 "A slight change in apparatus accounts for the difference in yield as shown here and as shown in Run D of Example 2.

EXAMPLE 4 BLOWING CONDITIONS Yield, Time, Hrs

Run No. F Air Cu Ft/Hr/Lb H 600 2.0 7s 18 I 575 2.7 78 22 J 550 3.4 72 I9 EXAMPLE 5 This example illustrates the high yields which can be obtained using our process. Two runs were made using as the feedstock a residue, from the catalytic cracking of gas oils, having a specific gravity of 1.0986 and containing 92 weight percent aromatics.

Using a five-gallon still, the feedstock was blown with air at a rate of 2.64 cu ft/lb charge/hour. The overhead vapor was refluxed using an ice water bath. A small amount of vapor (2-5 percent of the charge) escaped to the atmosphere. The greater loss was obtained on the run using the longer air blowing time (225F softening point pitch). The yield, blowing time and physical properties of the product obtained on each of the runs is shown below.

Run A Run B Yield, weight percent 95.6 98.] Air blowing time, min. 415 255 Softening point, "F i 225 l57.5 Penetration at 77F, O.l min. 0 5 Flash point, F COC 365 375 Thus, having described the invention in detail, it will be understood by those skilled in the art that certain variations and modifications may be made without departing from the spirit and scope of the invention as defined herein and in the appended claims.

We claim:

1. In a process for preparing petroleum pitch by air blowing of residues produced by the catalytic cracking of gas Oils, the improvements which comprise (1) use, as a feedstock, of residues having a specific gravity above 1.040 and containing at least weight percent aromatics and (2) the process is conducted in a manner such that not more than about 10 weight percent, based on the feedstock, of the vapors boiling above about 250F, resulting from the air blowing operation, are vented.

2. The process of claim 1 wherein it is conducted at a temperature of about 375 to about 650F and an air blowing rate of about 0.01 to about 5.0 cu ft per hour per pound of feedstock.

3. The process of claim 2 wherein the residue, used as feedstock, has a specific gravity of at least 1.076.

4. The process of claim 3 wherein not more than 10 weight percent of the vapors boiling above about 250F., resulting from the air blowing operation, are vented due to (a) use of a partial reflux condenser over the reaction vessel or (b) passing the effluent air and vapors through an external partial condenser and returning the condensed vapors to the reaction vessel.

5. The process of claim 3 wherein not more than about 5 weight percent of the vapors boiling above about 250F., resulting from the air blowing operation, are vented.

6. The process of claim 5 wherein not more than 5 weight percent of the vapors boiling above about 250F., resulting from the air blowing operation, are vented due to (a) use of a partial reflux condenser over the reaction vessel or (b) passing the effluent air and vapors through an external partial condenser and returning the condensed vapors to the reaction vessel.

7. The process of claim 6 wherein the residue, used as feedstock, has a specific gravity of at least l.09.

8. The process of claim 3 wherein not more than about 2 weight percent of the vapors boiling above about 250F., resulting from the air blowing operation, are vented.

9. The process of claim .8 wherein not more than 2 weight percent of the vapors boiling above about 250F., resulting from the air blowing operation, are

vented due to (a) use of a partial reflux condenser over the reaction vessel or (b) passing the effluent air and vapors through an external partial condenser and returning the condensed vapors to the reaction vessel.

10. The process of claim 9 wherein the residue, used as a feedstock, has a specific gravity of at least 1.09.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,909,389

DATED September 30, 1975 v T R(5) Paul J. Ruckel and Melvin M. McFeeters It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 14, insert per pound-- after per hour Signed and Scaled this twenty-fourth Day Of February 1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissiuner oflarents and Trademarks 

1. IN A PROCESS FOR PREPARING PETROLEUM PITCH BY AIR BLOWING OF RESIDUES PRODUCED BY THE CATALYTIC CRACKING OF GAS OILS, THE IMPROVEMENTS WHICH COMPRISE (1) USE, AS A FEEDSTOCK, OF RESIDUES HAVING A SPECIFIC GRAVITY ABOVE 1.040 AND CONTAINING AT LEAST 85 WEIGHT PERCENT AROMATICS AND (2) THE PROCESS IS CONDUCTED IN A MANNER SUCH THAT NOT MORE THAN ABOUT 10 WEIGHT PERCENT, BASED ON THE FEEDSTOCK, OF THE VAPORS BOILING ABOVE ABOUT 250*F, RESULTING FROM THE AIR BLOWING OPERATION, ARE VENTED.
 2. The process of claim 1 wherein it is conducted at a temperature of about 375* to about 650*F and an air blowing rate of about 0.01 to about 5.0 cu ft per hour per pound of feedstock.
 3. The process of claim 2 wherein the residue, used as feedstock, has a specific gravity of at least 1.076.
 4. The process of claim 3 wherein not more than 10 weight percent of the vapors boiling above about 250*F., resulting from the air blowing operation, are vented due to (a) use of a partial reflux condenser over the reaction vessel or (b) passing the effluent air and vapors through an external partial condenser and returning the condensed vapors to the reaction vessel.
 5. The process of claim 3 wherein not more than about 5 weight percent of the vapors boiling above about 250*F., resulting from the air blowing operation, are vented.
 6. The process of claim 5 wherein not more than 5 weight percent of the vapors boiling above about 250*F., resulting from the air blowing operation, are vented due to (a) use of a partial reflux condenser over the reaction vessel or (b) passing the effluent air and vapors through an external partial condenser and returning the condensed vapors to the reaction vessel.
 7. The process of claim 6 wherein the residue, used as feedstock, has a specific gravity of at least 1.09.
 8. The process of claim 3 wherein not more than about 2 weight percent of the vapors boiling above about 250*F., resulting from the air blowing operation, are vented.
 9. The process of claim 8 wherein not more than 2 weight percent of the vapors boiling above about 250*F., resulting from the air blowing operation, are vented due to (a) use of a partial reflux condenser over the reaction vessel or (b) passing the effluent air and vapors through an external partial condenser and returning the condensed vapors to the reaction vessel.
 10. The process of claim 9 wherein the residue, used as a feedstock, has a specific gravity of at least 1.09. 